A vacuum transfer system is a system in which a vacuum pump is actuated using compressed air so as to discharge air to the outside from the inside of a vacuum cup, thereby holding and transferring an article to a predetermined position using the resulting negative pressure. In this system, the vacuum cup is coupled with a separate pipe-shaped body to form a vacuum cup assembly, and is connected to the vacuum pump by means of the body.
FIG. 1 illustrates a conventional vacuum cup assembly 1. A vacuum cup 2 includes a ring-shape fastener having a flange 4 that protrudes outwards, and a flexible suction pad 5 which is joined to the side surface of the fastener while surrounding the flange 4. The fastener 3 is formed from a rigid material such as metal, plastic, etc., and the suction pad 5 is fixed to the fastener 3 by an adhesive or an insert-molding method.
The pipe-shaped body 6 is provided separately from the vacuum cup 2, and the fastener 3 of the vacuum cup 2 is coupled to a lower end of the body 6, thereby forming a vacuum cup assembly composed of the vacuum cup 2 and the body 6. Here, the inner space S of the suction pad 5 is in communication with a central passage 7 of the body 6. Thus, when the vacuum pump is actuated, the inside air of the vacuum cup 2 is evacuated and a negative pressure is concurrently created to hold an article in the inner space S.
Actually, the vacuum cup assembly 1 or vacuum cup 2 that has been used is the currently available one. However, after a period of use, the fatal problems occur of a gap partially forming between the fastener 3 and the suction pad 5 so that external air is introduced therethrough. Further, there are additional problems described below. It is assumed that such problems are the result of the method of joining the suction pad 5.
As well known in the art, the suction pad 5 is made of a flexible material such as silicone, urethane, rubber, etc. This material has improved adhesion or ability to create a seal with a smooth surface, so that it is applicable to a vacuum suction pad. On the contrary, that material also has the drawbacks of poor wear resistance and durability. Thus, damaged suction pads 5 frequently have to be replaced with new ones.
However, since the suction pad 5 was fixed in a joining manner as previously described, it could not be easily removed from or mounted to the fastener 3. In consideration of the structure, if the suction pad 5 is damaged, then the vacuum cup itself should be removed from the assembly 1. However, this causes the following problems:
First, despite the fastener 3 not having been damaged at all, the vacuum cup should be removed, causing monetary loss; and
Second, particularly when the occupied space is small, it is difficult to remove and mount the vacuum cup 2.
It appears though that these problems can be resolved by excluding the defective joining method with respect to the suction pad 5 and adapting a ‘fastening’ method using such as a bolt or the like. However, also in this case, the vacuum cup 2 can by no means be easy to remove and mount. Moreover, since in a region where the fastening is performed, the pad is subjected to deformation or damage by the load of an article, this method is determined to be unsuitable to a field of vacuum technology. In fact, the fastening method using e.g. bolts has been used as a supplementary measure for the joining method.